What this tool does
BMR is an estimate of calories used at complete rest — not a training day, not fidgeting, not digestion of a large meal. Protealpes reports Mifflin-St Jeor as the default and Harris-Benedict (Roza & Shizgal, 1984) as a comparison on the same height, weight, age, and sex inputs.
How it works
You enter sex, age, height, and weight. Mifflin-St Jeor is a linear equation fitted on adults in 1990 and is widely used because it tends to beat older Harris-Benedict in mixed groups. Neither equation knows muscle mass, thyroid status, or last night’s sleep.
Formula and methodology
Mifflin-St Jeor (1990): 10×weight(kg) + 6.25×height(cm) − 5×age + 5 (men) or − 161 (women). Revised Harris-Benedict (1984) uses different intercepts and slopes and is shown only as a second opinion. Typical disagreement of ~50–150 kcal is normal, not a scandal.
How to interpret the result
If BMR is 1,780 kcal, eating 1,780 kcal while commuting and training is a deficit. Use the TDEE calculator to put movement back in. Large gaps versus a wearable “resting” figure usually mean different definitions, not a broken organ.
Example
A 65 kg, 165 cm, 30-year-old woman: Mifflin-St Jeor BMR ≈ 1,370 kcal. That is overnight-plus-lying-still math. Her moderate TDEE is near 2,120 kcal. Planning meals at 1,370 kcal because “that’s my metabolism” is how people undershoot without meaning to.
Common mistakes
- Eating at BMR on purpose and calling it maintenance.
- Assuming a higher Harris-Benedict number means you “found” extra calories to cut.
- Using a child’s or older-adult clinical equation in place of this adult form.
- Comparing BMR across people without noticing height and weight differences.
When this estimate may be off
- Very high muscle mass or very high fat mass — the equation only sees total weight.
- Recent extreme dieting, illness, or drugs that change resting expenditure.
- Age or anthropometrics outside the adult range the fit was built on.
- You need a measured RMR (indirect calorimetry), which this page does not perform.